Fix and enable gating on H403

Fix occurrences of
H403 - multi line docstring end on new line

Change-Id: I79a818095e9f64a18ded1686fb152b9d58f3c8b1

cinder/volume/manager.py

@@ -135,7 +135,8 @@ class VolumeManager(manager.SchedulerDependentManager):
 
     def init_host(self):
         """Do any initialization that needs to be run if this is a
-           standalone service."""
+           standalone service.
+        """
 
         ctxt = context.get_admin_context()
         self.driver.do_setup(ctxt)